From: Oleg Nesterov Date: Tue, 5 Feb 2008 06:27:23 +0000 (-0800) Subject: __group_complete_signal(): fix coredump with group stop race X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=198466b41d11dd062fb26ee0376080458d7bfcaf;p=deliverable%2Flinux.git __group_complete_signal(): fix coredump with group stop race When __group_complete_signal() sees sig_kernel_coredump() signal, it starts the group stop, but sets ->group_exit_task = t in a hope that "t" will actually dequeue this signal and invoke do_coredump(). However, by the time "t" enters get_signal_to_deliver() it is possible that the signal was blocked/ignored or we have another pending !SIG_KERNEL_COREDUMP_MASK signal which will be dequeued first. This means the task could be stopped but not killed. Remove this code from __group_complete_signal(). Note also this patch removes the bogus signal_wake_up(t, 1). This thread can't be STOPPED/TRACED, note the corresponding check in wants_signal(). Signed-off-by: Oleg Nesterov Cc: Davide Libenzi Cc: Ingo Molnar Cc: Robin Holt Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/signal.c b/kernel/signal.c index 4333b6dbb424..ea90c34e9348 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -911,27 +911,6 @@ __group_complete_signal(int sig, struct task_struct *p) } while_each_thread(p, t); return; } - - /* - * There will be a core dump. We make all threads other - * than the chosen one go into a group stop so that nothing - * happens until it gets scheduled, takes the signal off - * the shared queue, and does the core dump. This is a - * little more complicated than strictly necessary, but it - * keeps the signal state that winds up in the core dump - * unchanged from the death state, e.g. which thread had - * the core-dump signal unblocked. - */ - rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending); - rm_from_queue(SIG_KERNEL_STOP_MASK, &p->signal->shared_pending); - p->signal->group_stop_count = 0; - p->signal->group_exit_task = t; - p = t; - do { - p->signal->group_stop_count++; - signal_wake_up(t, t == p); - } while_each_thread(p, t); - return; } /* @@ -1762,15 +1741,6 @@ static int handle_group_stop(void) { int stop_count; - if (current->signal->group_exit_task == current) { - /* - * Group stop is so we can do a core dump, - * We are the initiating thread, so get on with it. - */ - current->signal->group_exit_task = NULL; - return 0; - } - if (current->signal->flags & SIGNAL_GROUP_EXIT) /* * Group stop is so another thread can do a core dump,